Load-responsive brake force regulators which are actuated by way of a lever and a spring must be adapted to the special conditions of the vehicle into which they will be installed. One vehicle-related quantity is the distance between the attachment of one spring end on the vehicle and the actuating lever. An adjustment of this type is e.g. effected by a pin which extends between the lever and the other spring end and is attached to the lever, on one side, and to the spring, on the other side. One of the two attachments is axially displaceable on the pin. Thus, a correct pin length can be adjusted in conformity with the vehicle conditions. Care should be taken when adjusting the pin length that the lever is in its stop position on the control valve without clearance. Previously, this action has frequently been carried out manually by maintaining the lever in abutment until the second attachment is fixed. In a case of negligence, however, faults may occur in the correct adjustment of the pin length if the lever has not adopted its due position when the attachment is effected.
EP patent No. 0 486 342 teaches providing the variable attachment on the end of the pin close to the lever. The pin projects through the fixing device and has a compression spring on its other end which acts upon the pin, on the one hand, and on the fixing device, on the other hand. The fixing device, in turn, acts upon the lever. A compression spring of this type automatically ensures that the lever is urged to adopt its preset clearance-free position. The projecting end of the pin must be provided with a nominal breaking point so that, after adjustment of the pin length has been made, the now redundant end piece of the pin along with the spring can be removed. This permits re-use of the clearance compensation spring after the fixation for further brake force regulators.
It may occur, however, that careless manipulation in the assembly or excessive vibrations during transport cause breaking of the pin end already prior to the fixation of the pin length. This necessitates complicated mending operations. At least, replacement of the entire pin is necessary before of the brake force regulator can be installed into a vehicle.
An object of the present invention is to provide a brake force regulator of the type mentioned hereinabove which features inexpensive automatic clearance compensation for the actuating lever and is insensitive to vibrations already prior to the adjustment.
Consequently, the principle of the present invention includes using a simple and inexpensive rubber band as a clearance compensation element. According to the present invention, bands of elastomeric material are referred to as rubber band. A major dispersion of the tensile forces of the rubber bands used can easily be accepted for the mere clearance compensation. When the rubber band is premounted such that it cannot be removed after the adjustment, it may simply be dissected, if its removal is necessary at all. Thus, the pin cannot break, not even if manipulation is incorrect, because there is no nominal breaking point.
For noise-dampening purposes or for centering the control pistons, it is conventional practice to provide further compression springs on a pressure member which act upon the actuating lever so that it is urged away from the housing of the brake force regulator. In order to compensate these spring forces as well, the rubber band is rated so as to be able to overcome springs of this type.
When the rubber band is stretched between a lever-side fixing device on a pin, which is connected rigidly to the lever-side end of an actuating spring configured as a tension spring, and the spring winding which is most remote from the lever, the tensile force of the rubber band may even exceed that of the tension spring because the latter cannot be stretched by the rubber band. Additionally, the rubber band is easily removable without being damaged after mounting into the vehicle.
When the rubber band is stretched between the said fixing device and a shoulder disposed at the pin described hereinabove, the rubber band must be weaker than the tension spring. However, after fixation of the fixing device, the rubber band will not exert any force on the tension spring and may thus remain in the vehicle.
Integral manufacture of the pin and the actuating spring reduces assembly and material costs.